Question

A boy throws a stone vertically upward from a bridge , which is 20 m above the surface of water . The stone strikes the water surface 8 s after it's release. Calculate the speed by which the stone was thrown up ?​

Answer 1

ANSWER

Initial velocity of the stone u=−4.9m/s (upwards)

Acceleration of the stone g=9.8m/s

2

(downwards)

Time taken by the stone to fall down in water t=2 s

Height of the bridge H=ut+

2

1

gt

2

(Taking downward direction to be positive)

∴ H=(−4.9)(2)+

2

1

(9.8)(2)

2

=9.8 m

solution